You need to learn how the US system works first.
Firstly college in the US means university (specifically undergraduate studies, or generally the/a university).
As above you need an undergraduate degree to apply directly to medical school anywhere in the US as medicine is a postgraduate degree only there.
You do not need an undergad degree from Harvard to go to medical school there. Due to the premed coursework requirements you functionally do need to study your undergrad in the US, as you need 2 semesters of biology, 4 of chemistry though to organic chemistry (the final semester can or sometimes must be biochemistry), 2 semesters of physics, and usually 2 semesters of calculus and/or stats, AND at least one year studying science in an accredited US college. The only UK uni you can take that combination of subjects is Cambridge natsci, and even that will not fulfill the need to do a year of science classes in the US.
Both undergraduate studies and medicine are extremely expensive in the US and for the latter especially there is extremely limited funding available. In either case SFE will not find degrees abroad and the US federal funding does not find international students (much as sfe here doesn't). Therefore you need to have either around half a million dollars lying around in cash for the full trip, or for the undergrad get a scholarship, or apply to a college that commits to meeting all demonstrated financial need and ideally is need blind (which is basically just the extremely competitive elite college). And then figure out how to fund medical school there.
Basically the amount of effort and the level of excellence you need to demonstrate through academics and extracurriculars to get into a college in the US such that you can afford to study there for undergrad, much less the medical degree, is such that you would most likely be an extremely strong applicant for medicine in the UK anyway.
Also bear in mind even if you do get a medical degree in the US, that does not confer right to work in the US. In order to be sponsored for a working visa in the US, the sponsoring employer needs to demonstrate there are no suitable qualified American applicants for the job. Therefore, even aside from various other reasons, you would be pretty much limited to only non-competitive specialties like psychiatry, family medicine, or rural medicine and all in probably reasonably rural areas.
Essentially in almost no world is this likely if even feasible, and even if you did manage it then your dreams of presumably becoming a multimillion dollar earning surgeon in a big city (which is the only reason I can assume anyone is interested in practicing medicine in the US since their healthcare system is beyond broken, not to mention their education system and postgraduate medical training demands expecting you to have 36 hour shifts and work 100+ hour weeks) is not going to happen anyway due to how the visa situation plays out.
So you would be best off just pursuing medicine in the UK, honestly.